Time domain reflectometry as a tool for the estimation of quality in foods

The EU 5thFramework project 'SEQUID' aims, by measuring and analysing different seafoods during different storage conditions, to develop an instrument which will allow the determination of quality or freshness of fish and fish products. This is achieved by first measuring the time domain response of the samples to an input step pulse (rise time 60 ps) delivered to the surface of the samples by an open ended coaxial probe. The time domain data are then transformed, along with any other relevant variables such as temperature or artificial nose responses, using multivariate analysis, for example principal component analysis (PCA). The PC scores can then be used in regression equations or discriminant analysis. Results are presented which show how different quality aspects such as time of storage (chilled or frozen), temperature of storage, or sensory attributes can be predicted. It is also shown how the data can be used to categorise samples into different quality groups (eg once or twice frozen).